Health care faces many of the same barriers that other industries have faced in striving toward ultrasafety. However, health care must accommodate at least 3 additional industry-specific factors. First, risks in health care are not homogeneous. In many clinical domains, such as trauma surgery, the rate of serious complications is 1 × 10−2, but not all complications are related to medical errors (44). Rather, the risks are inherent in the clinical circumstances. In contrast, some health care sectors, such as gastroenterologic endoscopy, are inherently very safe, with a risk for serious adverse events of less than 1 × 10−5 per exposure. Second, the magnitude and impact of human error are unclear in medicine. Fundamentally, 3 risks are combined in health care: that of the disease itself, that entailed by the medical decision, and that of implementing the selected therapy. These 3 risks generally do not move in the same direction. This complexity makes error prevention harder to predict and grasp. The prognosis for a terminally ill patient may change because of an audacious surgical strategy. However, the most audacious strategies are less evenly distributed in the profession, are the most demanding technically, and are the most prone to errors. Finally, the risk for personal harm, such as becoming infected with HIV, weighs on the clinical staff in a unique way.